In U.S. Pat. No. 3,877,664, a device of this type is described including an upper perforated plate and a resisting framework comprising pillars and T-shaped sections for supporting this plate. This structure is integrated into the platform in such a way as to provide continuity between the two surfaces. The perforated plate rests on an annular support flange and the assembly perforated plate/pillars/sections constitutes an elastically deformable hanged structure, capable to absorb loads equivalent to the maximum loads to which the platform itself may be subjected. The pillars and the T-shaped sections are designed to ensure only a bending-strength generated by the load by a distribution of the strengths on the total assembly. However, this device exhibits two disadvantages.
Firstly, it means cutting a hole in the platform, and it can be seen that when the platform is the deck of a ship, this factor must be taken into account from the very design stage of the ship. Moreover, this cutout will inevitably affect the strength of the deck.
Secondly, it has been found that for engines weighing more than thirteen tons, it is not possible to use this device as such, even if it is attached directly to the platform, because this hanged assembly is not built to offer resistance against crushing stresses on the platform.
Pat. No. GB-A-1 117 751, describes a device for receiving and fastening a helicopter on the deck of a ship; but it is a system of bars, the ends of which are bolted on a roughly vertical support. This system cannot be used with heavy vehicles with weights of the order of thirteen tons, and has not been manufactured industrially.